Rattlegore is a bone golemmini-boss in Scholomance. He is directly under the Great Ossuary (Plagued Hatchling room) near Jandice Barov's dungeon (you can enter through the stairs or just fall through the holes in the hatchling room, but that is not recommended). Do note that if you do not empty the room of some patrolling mobs, you might over-pull, which does a lot during a boss fight. Have a priest ready to Shackle Undead just in case. While you possibly do not need to clear the whole room to fight Rattlegore, doing so is strongly advised, particularly if an attempt is being made to solo him at level 70 or below.

Unless you're a Paladin or a Warrior, Rattlegore probably should not be soloed in less than tier 4 (level 70) equivalent gear, because in terms of scaling, at less than that mitigation/stamina level, he hits like a truck.

This is also the room where the Paladin epic mount quest boss is located.